Yarn tension and break detector apparatus

ABSTRACT

An apparatus for detecting variations in tension and occurrences of breaks in a yarn traveling along a predetermined path including magnetically actuatable switch means having an open position and a closed position and being biased toward an open position and magnet means for magnetically influencing and normally maintaining the switch means in a closed position against its bias. Magnetic shunt means is carried by a yarn engaging means which moves under the influence of the yarn upon variations in tension and occurrences of a break in the yarn to move the shunt means into a position for shunting the influence of the magnet means on the switch means so that the switch means will shift under its bias to an open position.

United States Patent William D. Porter;

Bert B. Morgan, both of Asheville, N.C. 2,456

Jan. 13, 1970 Oct. 12, 197 1 Northrop Carolina, Inc.

Asheville, N.C.

[72] inventors [21] Appl. No. [22] Filed [45] Patented [73] Assignee [54] YARN TENSION AND BREAK DETECTOR 3,227,833 1/1966 Daviesetal.

ZOO/61.18

335/205 ZOO/61.18

ABSTRACT: An apparatus for detecting variations in tension and occurrences of breaks in a yarn traveling along a predetermined path including magnetically actuatable switch means having an open position and a closed position and being biased toward an open position and magnet means for magnetically influencing and normally maintaining the switch means in a closed position against its bias. Magnetic shunt means is carried by a yarn engaging means which moves under the influence of the yarn upon variations in tension and occurrences of a break in the yarn to move the shunt means into a position for shunting the influence of the magnet means on the switch means so that the switch means will shift under its bias to an open position.

PATENIEDHCI 1 2 I97l INVENTOR$ w\ LLIAM b. PORTEiZand; V B T B, MORGAN wwzmdymd ATTORNEYS:

YARN TENSION AND BREAK DETECTOR APPARATUS This invention relates to an apparatus for use with a textile machine and more particularly to an apparatus for detecting predetermined variations in tension and occurrences of breaks in a yarn traveling along a predetermined path of travel through a textile machine.

In yarn processing, such as warping or beaming, sizing, etc., yarn is continuously advanced along a predetermined path of travel through an appropriate textile machine wherein it is desirable to maintain tension on the yarn within predetermined limits. For instance in warping, if certain of the yarns are collected on the warp beam under excessive or insufficient tension, fabric produced from the warp would be of poor quality because of the extreme variations in tension on individual yarns within the fabric. Thus, it is readily apparent that it is desirable to detect variations in tension on the yarn outside predetermined limits so that such variations may be corrected. Similarly, when a yarn breaks, the occurrence of the break must be detected so that the break may be repaired.

Numerous apparatus have heretofore been provided for detecting predetermined variations in tension and occurrences of breaks in yarn traveling along a predetermined path of travel through a textile machine. However, these apparatus have not proven to be entirely satisfactory for one or more reasons. For instance, many of the apparatus are capable of detecting only the occurrence of a break in the yarn while others are capable of detecting only insufficient tension and the occurrence of a break in the yarn. In addition, many of these apparatus involve complicated mechanical switching means which require a large amount of space. Furthermore, the mechanical switching means is normally associated with movement of a yarn engaging member in response to variations in tension of the yarn which switching means often presents malfunction problems.

Thus, it is an object of the present invention to provide a simple, efficient apparatus for detecting excessive tension, insufficient tension and occurrences of breaks in a yarn traveling along a predetermined path of travel through a textile machine and which apparatus avoids mechanical switching and a large space requirement.

By this invention, it has been found that the above object may be accomplished by providing a magnetically actuatable switch means having an open position and a closed position and being biased toward one of the positions, preferably the open position. Magnetic means is disposed in spaced relation from the switch means for magnetically influencing and normally maintaining the switch means in the other of the positions against its bias. A yarn engaging means is provided for moving a predetermined distance under the influence of the yarn from a normal position in accordance with predetermined variations in tension of the yarn and the occurrence of a break in the yarn and has shunt means carried thereby for movement therewith to a position for shunting the magnetic influence of the magnet means to the switch means when the yarn engaging means is moved a predetermined distance whereby the switch means will shift under its bias to the one position.

Preferably, the yarn engaging means is movable under the influence of the yarn from a normal position in opposite, alternative first and second directions in accordance with predetermined variations in the tension of the yarn and the occurrence of a break in the yarn and has spaced apart shunt means carried thereby for alternative movement therewith. One of the shunt means moves into a position between the magnet means and switch means when the yarn engaging means moves in either of the first and second directions for shunting the magnetic influence of the magnet means to the switch means whereby the switch means will shift under its bias to the one position. In addition, the apparatus, preferably, includes weight means operatively connected to the yarn engaging means for biasing the yarn engaging means and spaced apart shunt means in one of the first and second directions and for applying a predetermined tension to the yarn.

The switch means is preferably a reed switch and comprises a pair of elongate, flexible, magnetic, biased apart switch contacts disposed in parallel relation and having overlapping end portions.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds, when taken in connection with the accompanying drawings, in which: s

FIG. 1 is a schematic, perspective view illustrating an apparatus of the present invention;

FIG. 2 is a schematic, exploded, perspective view with portions removed of the apparatus of FIG. 1;

FIG. 3 is an enlarged, partial, sectional view taken substantially along the line 3-3 of FIG. 1;

FIG. 4 is an enlarged, schematic, plan view with parts in section and other parts broken away of the apparatus of FIG. 1 illustrating the position of various components thereof when the tension in the yarn is outside predetermined limits; and

FIG. 5 is a schematic view of the apparatus of FIG. 1 with parts in section illustrating the positions of various components thereof when the tension in the yarn is within predetermined limits and schematically illustrating circuit means associated therewith.

Referring specifically to FIGS. 1 and 2, there is illustrated an apparatus, generally designated at 10, constructed in accordance with the present invention for detecting predetermined variations in tension and the occurrence of breaks in a yarn Y traveling along a predetermined path of travel through any suitable textile machine (not shown) over spaced-apart guide bars 11 and 12.

The apparatus 10 includes a housing, generally designated at 15, formed of a suitable nonmagnetic and preferably nonelectric conductive material such as plastic and the like and which comprises a generally rectangular body or frame 16 as best illustrated in FIG. 2. The body 16 has a pair of communicating slots or grooves 18 and 19 disposed on one side thereof substantially perpendicular to each other and extending the width thereof.

The body 16 additionally includes a pair of spaced pockets 2] and 22, pocket 22 being substantially larger than pocket 21, disposed in opposite sides of body 16 with pockets 21 and 22 being disposed on opposite sides of groove 19 (for reasons to be hereinafter explained) but not communicating therewith. A face plate 23 is attached to the side of body 16 having slots or grooves 18 and 19 by any suitable means such as nut and bolt assemblies 24 extending through cooperating apertures 25 and 26 in the body 16 and the face plate 23, respectively. The nut and bolt assemblies 24 may additionally be employed, as illustrated in FIG. 1, to secure the housing 15 to a suitable supporting structure 27. The face plate 23 closes the sides of grooves 18 and 19 so that body 16 and face plate 23 cooperate to define a guideway formed by grooves 18 and 19 extending through housing 15 having a generally L-shaped cross-sectional shape. The housing 15 is mounted beneath guide bars 11 and 12 on supporting structure 27 with the guideway formed by slots or grooves 18 and 19 being vertically aligned between the horizontally spaced-apart guide bars 1 1 and 12 (for reasons to be hereinafter explained).

A magnetically actuatable switch means, preferably a reed switch, generally indicated at 30, of any suitable construction, is mounted within pocket 22 parallel with slots or grooves 18 and 19 and between sidewall 31 of pocket 22 and projection 32 which extends from end wall 33 of pocket 22 outwardly into pocket 22 (as best illustrated in FIGS. 2 and 3). The reed switch 30 has an open position and a closed position and comprises a pair of elongate, flexible, magnetic, biased-apart switch contacts 34 and 35 disposed in parallel relation with each other and having overlapping end portions. The contacts 34 and 35 are encapsulated and sealed within an elongate casing 36 of a nonmagnetic, nonelectric conductive material such as glass or the like for protecting the contacts 34 and 35 from humidity and other atmospheric conditions which might affect the operation of the reed switch 30. One of the switch contacts is mounted through one end of the casing 36 and the other switch contact is mounted through the other end of the casing 36 such that appropriate circuit means (to be hereinafter described) may be operatively connected with the switch contacts 34 and 35.

A magnetic flux producing means, generally indicated at 40, in the form of a permanent magnet of generally bar shape having a north pole and a south pole designated respectively by the letters N and S adjacent opposite ends thereof is mounted in pocket 21 on the other side of slots or grooves 18 and 19 in opposed relation to reed switch 30. Magnet 40 is of sufficient strength to create magnetic lines of flux (as indicated schematically in FIGS. 2, 4 and for magnetically influencing and normally maintaining the contacts 34 and 35 closed against their open bias by causing the overlapping end portions of magnetic switch contacts 34 and 35 to be rendered magnetic and mutually attracted toward each other. While a permanent magnet 40 is here illustrated and preferred, it will be apparent that other conventional magnet means may be employed, such as an electromagnet of conventional construction.

An elongate plunger means, generally designated at 50, is provided and comprises eyelet means 51 in the form of an elongate wire having an eyelet 52 disposed in the end thereof for receiving therethrough the yarn Y (FIG. 1) and an elongate angle member 53 having a generally L-shaped cross section corresponding to the cross section of the guideway formed by slots or grooves 18 and 19. The angle member 53 is connected at one end to eyelet means 51 and is disposed through the guideway formed by slots or grooves 18 and 19 for movement therein through the housing between reed switch 30 and permanent magnet 40 in opposite alternative first and second directions substantially perpendicular to the path of travel of yarn Y.

When yarn Y is threaded through the eyelet 52 of eyelet means 51, the weight of the plunger means 50 creates a tension on the yarn Y (as illustrated in FIG. 1) such that the plunger means 50 will be biased in one of the first and second directions and will be movable underthe influence of the yarn Y in accordance with variations in the tension of the yarn Y and the occurrence of a break in the yarn Y. More particularly, should the tension in the yarn Y become excessive the plunger means 50 will be vertically raised in a first direction and should insufiicient tension exist in the yarn Yor the yarn Y break, the plunger means 50 will be lowered vertically in an opposite, second direction. The angle portion 53 of plunger means 50 includes abutment means 54 for engaging housing 15 to prevent plunger means 50 from falling from housing 15 as when the yarn Y breaks. Weight means 60 (as illustrated in FIG. 1) may be connected to the end of angle member 53 for additionally biasing the plunger means 50 vertically downward and for applying a predetermined tension to the yarn Y passing through the eyelet 52.

At longitudinally aligned, spaced-apart positions on angle member 52 of plunger means 50, shunt means 70 are provided in the form of elongate magnetic metal strips of high permeability, such as mu-metal which is a magnetic alloy of approximately 78 percent nickel or alloy of similar magnetic characteristics. With reference to FIGS. 1 and 2, the elongate magnetic metal strips of high permeability have a generally L- shaped cross-sectional shape and are mounted by any suitable means such as adhesive in receiving recesses of angle member 53 of plunger means 50. The angle member 53 of plunger means 50 is preferably formed of a nonmagnetic material, such as plastic and the like, so that the portion of the angle member 53 between the spaced-apart, elongate, magnetic, metal strips is nonmagnetic whereby the magnetic influence of pennanent magnet 40 is not shunted thereby when the portion is positioned in the guideway of housing 15 between the permanent magnet 40 and reed switch 30.

The apparatus 10 is so constructed and mounted on support structure 2 7 that when the tension in the yarn Y (FIG. 5) is within predetermined limits, the portion of angle member 53 between shunt means 70 is normally positioned in the guideway between permanent magnet 40 and reed switch 30 so that switch contacts 34 and 35 will be magnetically influenced by magnet 40 and be maintained in a closed position against an open bias. However, upon the tension in the yarn Y varying beyond predetermined limits, as determined by the spacing between shuntmeans 70, the plunger means 50 will move in either of the first or second directions under the influence of the yarn Y in accordance with the tension variation to move one of the magnetic metal strips between the reed switch 30 and magnet 40 (FIG. 4) for shunting the magnetic influence of magnet 40 to the reed shift 30 whereby the switch contacts 34 and 35 will be caused to shift under their bias to the biased-apart open position.

In accordance with the foregoing description, it will be apparent that the read switch 30 may be operatively connected by suitable circuit means to any suitable warning apparatus, stop motion apparatus, etc., which is responsive to shifts in position of the reed switch 30 for indicating that the tension in the yarn Y has varied beyond predetermined limits or that the yarn Y is broken. One suitable and preferred circuit means is schematically illustrated in FIG. 5 and comprises a bidirectional, semiconductor, gate-controlled, switching means, generally indicated at 80, such as a Triac, including a gate control element 81.

A Triac is a commercially available, gate controlled, bidirectional device manufactured and sold by compartment manufacturers, such as the General Electric Company. While a more detailed description of the characteristics of such a device can be obtained from technical literature available from manufacturers, such as the General Electric Company, it is believed that the following brief description is adequate for the purpose of this disclosure. A Triac can conduct current in either of two directions, depending upon the polarity of the potential across its load terminal 82 and 83 and is triggered in a conducting state by a low current gating signal applied to gate control element 81.

As illustrated in FIG. 5, the gate control element 81 which governs the triggering of Triac between conductive and nonconductive states, is operatively connected to reed switch 30. The load terminals 82 and 83 of Triac 80 are connected to suitable plug means 85 for facilitating the connection of apparatus 10 to suitable warning apparatus, stop motion apparatus, etc., generally designated at 90, and power source (not shown) for operation of both the apparatus 10 and the warning apparatus, stop motion, etc. Thus, when contacts 34 and 35 are closed, a gating signal will be applied to Triac 80 to trigger it into a conductive state and when contacts 34 and 35 are open, Triac 80 will be nonconductive. It can be appreciated that when contacts 34 and 35 are closed, the gating current that flows therebetween will be small in comparison to that flowing through Triac 80 to prolong the life of reed switch 30. To further decrease the current flow between contacts 34 and 35 and to limit the voltage and current of the gating signal, a register 86 is disposed in series with gate control element 81 and reed switch 30. Many other advantages are gained by the solid-state switching circuit described above including the elimination of arc erosion of contacts, contact bounce, etc., which will become apparent to one skilled in solid-state circuitry.

The circuit means described above including Triac 80, plug 85 and resistor 86 are also mounted within pocket 22 of body 16 (as illustrated in FIGS. 1 and 2) with plug 85 being disposed in a receiving slot 92 of body 16 for access thereto exterior to housing 15. To complete housing 15, pockets 21 and 22 are filled with a nonmagnetic, nonelectric conductive material 93 such as plastic or the like for maintaining the various components mounted therein in place.

In operation, the apparatus 10 is mounted beneath the predetermined path of travel of yarn Y in such a manner that the yarn Y may be received through eyelet means 52 of plunger means 50 with the yarn Y being deflected downwardly a predetermined extent from guide bars 11 and 12 in accordance with the tension in yarn Y and the weight of plunger means 50, shunt means 70, and weight means 60 such that the portion of angle member 53 between shunt means 70 is positioned in the guideway formed by slots or grooves 18 and 19 between reed switch and permanent magnet 40 (as shown in FIG. 5) so that switch contacts 34 and 35 will be magnetically influenced by permanent magnet and maintained in a closed position against an open bias. With plug 85 suitably connected to a warning apparatus or stop motion apparatus, etc., indicated at 90, and power source, not shown, Triac 80 will be in a conductive state for indicating that the tension in the yarn Y is within predetermined limits. However, should the tension in the yarn Y become excessive, plunger means will be raised upwardly in the first direction under the influence of the yarn Y to move the lower shunt means 70 between reed switch 30 and magnet 40 to shunt the magnetic influence of magnet 40 on reed switch 30. Reed switch 30 will then open to render Triac 80 nonconductive and thus, indicate that the tension in the yarn Y is outside of predetermined limits. Similarly, should the tension in the yarn Y become insufficient or the yarn Y break, the upper of the shunt means 70 will be moved between the reed switch 30 and magnet 40 to open reed switch 30 and render Triac 80 nonconductive and thus, indicate that the tension in the yarn Y is outside of predetermined limits.

In the drawings and specification there has been set forth a preferred embodiment of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

What is claimed is:

1. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising:

magnetically actuatable switch means having an open position and a closed position and being biased toward one of said positions,

magnet means disposed in spaced relation from said switch means for magnetically influencing and normally maintaining said switch means in the other of said positions against its bias,

means for engaging the yarn and for moving in opposite alternative directions a predetermined distance under the influence of the yarn from a normal position to abnormal positions in accordance with predetermined increased or decreased variations in the tension of the yarn and the oc' currence of a break in the yarn, and

shunt means carried by said yarn engaging means and disposed for movement therewith to positions for shunting the magnetic influence of said magnet means to said switch means when said yarn engaging means is moved whereby said switch means will shift under its bias to said one position.

2. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising:

magnetically actuatable switch means having an open position and a closed position and being biased toward one of said positions,

magnet means disposed in spaced relation from said switch means for magnetically influencing and normally maintaining said switch means in the other of said positions against its bias,

means for engaging the yarn and for moving a predetermined distance under the influence of the yarn from a normal position in opposite, alternative first and second directions to abnormal positions in accordance with predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn, and

spaced-apart shunt means carried by said yarn engaging means and disposed for alternative movement therewith into positions between said magnet means and said switch means when said yarn engaging mans moves in either of said first and second directions, the portion of said yarn engaging means between said spaced-apart shunt means being nonmagnetic and being normally positioned between said magnet means and switch means when said yarn engaging means is in said normal position and said switch means is in said magnetically influenced other position, so that one of said shunt means will be moved between said magnet means and switch means when said yarn engaging means is moved in either of said first and second directions for shunting the magnetic influence of said magnet means to said switch means whereby said switch means will shift under its bias to said one position.

3. An apparatus, as set forth in claim 2, wherein said yarn engaging means comprises an elongate plunger means having an eyelet means on one end thereof for receiving and allowing passage therethrough of the yarn.

4. An apparatus, as set forth in claim 3, including weight means for biasing said plunger means and said spaced-apart shunt means in one of said first and second directions and for applying a predetermined tension to the yarn passing through said eyelet means.

5. An apparatus, as set forth in claim 2, wherein said switch means includes a pair of elongate, flexible, magnetic, biasedapart switch contacts disposed in parallel relation and having overlapping end portions; and wherein said magnet means is a permanent magnet.

6. An apparatus, as set forth in claim 2, wherein said yarn engaging means comprises an elongate plunger means formed from a nonmagnetic material; and wherein said spaced-apart shunt means comprises two elongate, magnetic, metal strips of high permeability carried in longitudinally aligned, spacedapart positions on said plunger means.

7. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising:

a pair of elongate, flexible, magnetic, biased-apart switch contacts disposed in parallel relation and having over lapping end portions,

a permanent magnet disposed in spaced relation from said switch contacts for magnetically influencing and normally maintaining said switch contacts closed against their bias,

an elongate plunger means having an eyelet means on one end thereof for receiving and allowing passage therethrough of the yarn and for moving a predetermined distance under the influence of the yarn from a normal position in opposite, alternative first and second directions to abnormal positions in accordance with the predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn,

two elongate magnetic metal strips of high permeability carried in longitudinally aligned, spaced-apart relation on said plunger means and disposed for alternative movement therewith into positions between said magnet and said switch contacts when said plunger means moves in either of said first and second directions to said abnormal positions, and

the portion of said plunger means between said spacedapart, magnetic, metal strips being nonmagnetic and being normally positioned between said magnet and said switch contacts when said plunger means is in said normal position and said switch contacts are closed so that one of said magnetic, metal strips will be moved between said magnet and said switch contacts when said plunger means is moved in either of said first and second directions to said abnormal positions for shunting the magnetic influence of said magnet to said switch contacts whereby said switch contacts will shift under their bias to said biased-apart relation.

8. An apparatus, as set forth in claim 7, including an elongate casing of a nonmagnetic, nonelectric conductive material for encapsulating said switch contacts, one of said switch contacts being mounted in one end of said casing and the other being mounted in the other end of said casing.

9. An apparatus, as set forth in claim 7, including bidirectional, semiconductor, gate-controlled switching means operatively connected with said switch contacts for limiting current flow between said contacts when closed.

10. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising:

a nonmagnetic housing having an elongate guideway extending therethrough,

magnetically actuatable switch means having an open position and a closed position and being biased toward said open position and being mounted within said housing on one side of said guideway,

a permanent magnet mounted in said housing on the opposite side of said guideway in opposed relation to said switch means for magnetically influencing and normally maintaining said switch means in said closed position against its bias,

an elongate plunger means having an eyelet means on one end thereof for receiving and allowing passage therethrough of the yarn and being disposed in said guideway for sliding movement through said housing between said magnet and switch means under the influence of the yarn, said plunger means being movable a predetermined distance from a normal position in opposite, alternative first and second directions to abnormal positions in accordance with predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn,

' two elongate, magnetic, metal strips of high permeability carried in longitudinally aligned, spaced-apart relation on said plunger means for movement therewith through said housing and disposed for alternative movement therewith into positions between said magnet and switch means when said plunger means moves in either of said first and second directions to said abnormal positions, and

the portion of said plunger means between said spacedapart, magnetic, metal strips being nonmagnetic and being normally positioned between said magnet and switch means when said plunger means is in said normal position and said switch means is closed so that one of said magnetic, metal strips will be moved between said magnet and switch means when said plunger means is moved in either of said first and second directions to said abnormal positions for shunting the magnetic influence of said magnet to said switch means whereby said switch means will shift under its bias to said open position.

11. An apparatus, as set forth in claim 10, including weight means connected to the other end of said plunger means for biasing same in one of said directions and for applying a predetermined tension to the yarn passing through said eyelet means.

12. An apparatus, as set forth in claim 10, including an elongate casing of a nonmagnetic, nonelectric conductive material for encapsulating said switch means.

13. An apparatus, as set forth in claim [0, including bidirectional, semiconductor, gate-controlled switching means operatively connected with said magnetically actuatable switch means for limiting current flow therethrough when said switching means is closed.

14. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising:

magnetically actuatable switch means having an open position and a closed position and being biased toward one of said positions,

magnet means disposed in spaced relation from said switch means for magnetically influencing said switch means to the other of said positions against its bias, means for engaging the yarn and for moving in opposite alternative directions a predetermined distance under the influence of the yarn from a normal position to abnormal positions in accordance with predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn, and

shunt means for shunting the magnetic influence of said magnet means on said switch means and being carried by said yarn engaging mans for movement therewith to a position for changing the magnetic influence of said magnet means to said switch means when said yarn engaging means is moved thereby said switch means will shift to another of said positions.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 791 Dated October 12 1971 Inventor) William D. Porter and Bert B. Morgan It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 56, "52 should be -53-; Column 4, line 12, "shift" should read -switch-;

line 16, "read" should be -reed--;

line 27, "compartment" should be --component-; line 35, "terminal" should be -terminals-;

line 56, "register" should be --resistor-;

Column 6, line 1, "mans should be -means--; Column 8, line 39, "mans" should be -means.

Signed and sealed this 28th day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising: magnetically actuatable switch means having an open position and a closed position and being biased toward one of said positions, magnet means disposed in spaced relation from said switch means for magnetically influencing and normally maintaining said switch means in the other of said positions against its bias, means for engaging the yarn and for moving in opposite alternative directions a predetermined distance under the influence of the yarn from a normal position to abnormal positions in accordance with predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn, and shunt means carried by said yarn engaging means and disposed for movement therewith to positions for shunting the magnetic influence of said magnet means to said switch means when said yarn engaging means is moved whereby said switch means will shift under its bias to said one position.
 2. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising: magnetically actuatable switch means having an open position and a closed position and being biased toward one of said positions, magnet means disposed in spaced relation from said switch means for magnetically influencing and normally maintaining said switch means in the other of said positions against its bias, means for engaging the yarn and for moving a predetermined distance under the influence of the yarn from a normal position in opposite, alternative first and second directions to abnormal positions in accordance with predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn, and spaced-apart shunt means carried by said yarn engaging means and disposed for alternative movement therewith into positions between said magnet means and said switch means when said yarn engaging mans moves in either of said first and second directions, the portion of said yarn engaging means between said spaced-apart shunt means being nonmagnetic and being normally positioned between said magnet means and switch means when said yarn engaging means is in said normal position and said switch means is in said magnetically influenced other position, so that one of said shunt means will be moved between said magnet means and switch means when said yarn engaging means is moved in either of said first and second directions for shunting the magnetic influence of said magnet means to said switch means whereby said switch means will shift under its bias to said one position.
 3. An apparatus, as set forth in claim 2, wherein said yarn engaging means comprises an elongate plunger means having an eyelet means on one end thereof for receiving and allowing passage therethrough of the yarn.
 4. An apparatus, as set forth in claim 3, including weight means for biasing said plunger means and said spaced-apart shunt means in one of said first and second directions and for applying a predetermined tension to the yarn passing through said eyelet means.
 5. An apparatus, as set forth in claim 2, wherein said switch means includes a pair of elongate, flexible, magnetic, biased-apart switch contacts disposed in parallel relation and having overlapping end portions; and wherein said magnet means is a permanent magnet.
 6. An apparatus, as set forth in claim 2, wherein said yarn engaging means comprises an elongate plunger means formed from a nonmagnetic material; and wherein said spaced-apart shunt meAns comprises two elongate, magnetic, metal strips of high permeability carried in longitudinally aligned, spaced-apart positions on said plunger means.
 7. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising: a pair of elongate, flexible, magnetic, biased-apart switch contacts disposed in parallel relation and having overlapping end portions, a permanent magnet disposed in spaced relation from said switch contacts for magnetically influencing and normally maintaining said switch contacts closed against their bias, an elongate plunger means having an eyelet means on one end thereof for receiving and allowing passage therethrough of the yarn and for moving a predetermined distance under the influence of the yarn from a normal position in opposite, alternative first and second directions to abnormal positions in accordance with the predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn, two elongate magnetic metal strips of high permeability carried in longitudinally aligned, spaced-apart relation on said plunger means and disposed for alternative movement therewith into positions between said magnet and said switch contacts when said plunger means moves in either of said first and second directions to said abnormal positions, and the portion of said plunger means between said spaced-apart, magnetic, metal strips being nonmagnetic and being normally positioned between said magnet and said switch contacts when said plunger means is in said normal position and said switch contacts are closed so that one of said magnetic, metal strips will be moved between said magnet and said switch contacts when said plunger means is moved in either of said first and second directions to said abnormal positions for shunting the magnetic influence of said magnet to said switch contacts whereby said switch contacts will shift under their bias to said biased-apart relation.
 8. An apparatus, as set forth in claim 7, including an elongate casing of a nonmagnetic, nonelectric conductive material for encapsulating said switch contacts, one of said switch contacts being mounted in one end of said casing and the other being mounted in the other end of said casing.
 9. An apparatus, as set forth in claim 7, including bidirectional, semiconductor, gate-controlled switching means operatively connected with said switch contacts for limiting current flow between said contacts when closed.
 10. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising: a nonmagnetic housing having an elongate guideway extending therethrough, magnetically actuatable switch means having an open position and a closed position and being biased toward said open position and being mounted within said housing on one side of said guideway, a permanent magnet mounted in said housing on the opposite side of said guideway in opposed relation to said switch means for magnetically influencing and normally maintaining said switch means in said closed position against its bias, an elongate plunger means having an eyelet means on one end thereof for receiving and allowing passage therethrough of the yarn and being disposed in said guideway for sliding movement through said housing between said magnet and switch means under the influence of the yarn, said plunger means being movable a predetermined distance from a normal position in opposite, alternative first and second directions to abnormal positions in accordance with predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn, two elongate, magnetic, metal strips of high permeability cArried in longitudinally aligned, spaced-apart relation on said plunger means for movement therewith through said housing and disposed for alternative movement therewith into positions between said magnet and switch means when said plunger means moves in either of said first and second directions to said abnormal positions, and the portion of said plunger means between said spaced-apart, magnetic, metal strips being nonmagnetic and being normally positioned between said magnet and switch means when said plunger means is in said normal position and said switch means is closed so that one of said magnetic, metal strips will be moved between said magnet and switch means when said plunger means is moved in either of said first and second directions to said abnormal positions for shunting the magnetic influence of said magnet to said switch means whereby said switch means will shift under its bias to said open position.
 11. An apparatus, as set forth in claim 10, including weight means connected to the other end of said plunger means for biasing same in one of said directions and for applying a predetermined tension to the yarn passing through said eyelet means.
 12. An apparatus, as set forth in claim 10, including an elongate casing of a nonmagnetic, nonelectric conductive material for encapsulating said switch means.
 13. An apparatus, as set forth in claim 10, including bidirectional, semiconductor, gate-controlled switching means operatively connected with said magnetically actuatable switch means for limiting current flow therethrough when said switching means is closed.
 14. An apparatus for use in a textile machine for detecting predetermined increased or decreased variations in tension and occurrences of breaks in a yarn traveling along a predetermined path, said apparatus comprising: magnetically actuatable switch means having an open position and a closed position and being biased toward one of said positions, magnet means disposed in spaced relation from said switch means for magnetically influencing said switch means to the other of said positions against its bias, means for engaging the yarn and for moving in opposite alternative directions a predetermined distance under the influence of the yarn from a normal position to abnormal positions in accordance with predetermined increased or decreased variations in the tension of the yarn and the occurrence of a break in the yarn, and shunt means for shunting the magnetic influence of said magnet means on said switch means and being carried by said yarn engaging mans for movement therewith to a position for changing the magnetic influence of said magnet means to said switch means when said yarn engaging means is moved thereby said switch means will shift to another of said positions. 